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Date: Thu, 22 Sep 2005 16:59:29 +0200
From: Peter Menzebach <pm@mw-itcon.de>
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Cc: "Artem B. Bityutskiy" <dedekind@yandex.ru>, linux-mtd@lists.infradead.org
Subject: Re: data  loss on jffs2 filesystem on dataflash
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Andrew Victor wrote:
> hi,
Hi,
> 
>>>Problem is here, how does the user get the information about the erase 
>>>size used by jffs2?
>>
>>He detects that the flash is DataFlash (mtd->type == MTD_DATAFLASH). 
>>Afterwards he knows, that
>>1. mtd->erasesize is the size of DataFlash block
>>2. mtd->oobblock is the size of DataFlash page
> 
> 
> No.  You can't change mtd->erasesize.
> There are other existing applications that access the raw MTD layer and
> want the real erasesize.
I agree. The erase size reported to the mtd layer should be always the 
physical erase size (528/1056).

>>Sorry, didn't get it. I mean, MTD provide information about both 
>>DataFlash block size and DataFlash page size. That's obvious.
> 
> 
> This magic minimum block size could always be calculated in JFFS2 (in
> jffs2_dataflash_setup).  It is a JFFS2-specific value.
> Just calculate an 'N' where:
>    (N * mtd->erasesize) >= jffs2_minimum_block_size
> and
>    (mtd->size % (N * mtd->erasesize)) == 0

That would possible.
Set jffs2->wbuf_size to erasesize and calculate the jffs2->sector size 
as you outlined...

Best regards
Peter


-- 
Peter Menzebach
Menzebach und Wolff IT-Consulting GbR
Phone +49 751 355 387 1